The present invention relates to a floppy disk drive apparatus.
A floppy disk drive apparatus is known which shifts a magnetic head in the radial direction of a floppy disk fitted over a spindle, while rotating the floppy disk, and a data write/read operation is effected with respect to the floppy disk. The floppy disk drive apparatus of this type is adapted to control the operation of a motor for rotating the spindle and pulse motor for linearly moving a magnetic head, and is connected to a host computer for effecting a data write/read operation with respect to the floppy disk through the magnetic head. The apparatus includes a detector for optically detecting that the magnetic head is placed in a reference track position or a track zero position and is adapted to supply a track zero sinal to the host computer when motor drive signals in a predetermined phase relation are supplied to the pulse motor while an output signal is being generated from the detector. Since, in this case, the detector optically detects the position of the magnetic head, it cannot detect the track zero position of the magnetic head accurately. Where the pulse motor is a four-phase motor which is driven, for example, according to a 2-phase excitation method to cause the head to be moved by one track each time the phase of the motor drive signal varies, the motor drive signal comes to have the same phase relation each time the magnetic head is moved by four tracks. If an output signal is generated from the detector when the magnetic head is moved to a position four tracks away from the track zero position, there is a possibility that a track zero signal will be generated from the floppy disk drive apparatus to the host computer as the case may be. It is, therefore, required that the positional relation of the detector and magnetic head is accurately set to permit the detector to stop the generation of an output signal before the magnetic head is moved inwardly four tracks from the reference track position.
Recently, a double track system has been developed in which tracks are formed in high density. In this case, the rotation angle corresponding to one step of the pulse motor becomes one half, making it difficult to set the magnetic head and detector in place. Even in a floppy disk drive apparatus for generating two pulses to move the magnetic head by one track, it is difficult to correctly set a relative position between the magnetic head and the detector.